The present invention relates generally to chemical mechanical polishing of substrates and, more particularly to a polishing pad conditioner cleaning apparatus.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. Specific structures and devices are formed by preferential etching of the layers aided by photolithography. High resolution and accurate focusing of the photolithography apparatus allows the formation of well defined micro- or nano-structures. Accurate focusing of the photolithography apparatus is difficult for non-planar surfaces. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive, or insulative layer, to form a relatively flat, smooth surface.
Chemical mechanical polishing (CMP) is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head provides a controllable load, i.e., pressure, on the substrate to push it against the polishing pad. In addition, the carrier head may rotate to provide additional motion between the substrate and polishing surface. Further, a polishing slurry, including an abrasive and at least one chemically-reactive agent, may be spread on the polishing pad to provide an abrasive chemical solution at the interface between the pad and substrate.
The effectiveness of a CMP process may be measured by its polishing rate, and by the resulting finish (absence of small-scale roughness) and flatness (absence of large-scale topography) of the substrate surface. Inadequate flatness and finish can produce substrate defects. The polishing rate, finish and flatness are determined by the pad and slurry combination, the relative speed between the substrate and pad, and the force pressing the substrate against the pad. The polishing rate sets the time needed to polish a layer. Thus, it sets the maximum throughput of the polishing apparatus.
It is important to take appropriate steps to counteract any deteriorative factors which may either damage the substrate (such as by scratches resulting from accumulated debris in the pad) or reduce polishing speed and efficiency (such as results from glazing of the pad surface after extensive use). The problems associated with scratching the substrate surface are self-evident. The more general pad deterioration problems both decrease polishing efficiency, which increase cost, and create difficulties in maintaining consistent operation from substrate to substrate as the pad decays.
The glazing phenomenon is a complex combination of contamination, thermal, chemical and mechanical damage to the pad material. When the polisher is in operation, the pad is subject to compression, shear and friction producing heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects reduce the pad""s roughness and its ability to efficiently polish the substrate.
It is, therefore, desirable to continually condition the pad by removing trapped slurry, and unmatting or re-expanding the pad material.
A number of conditioning procedures and apparatus have been developed. A conventional conditioner has an arm holding a conditioner head with an abrasive disk facing the polishing pad. A bearing system rotatably supports the abrasive disk at the end of the arm. The abrasive disk rotates against the polishing pad to physically abrade the polishing pad and remove the glazing layer from the polishing pad.
While the abrasive disk is rotating against the polishing pad, slurry will tend to coat the conditioner head. However, when the conditioner head is not operating, e.g., between polishing operations or due to maintenance, the slurry on conditioner head will tend to dry out. As the slurry dries, it tends to form a hardened xe2x80x9ccakedxe2x80x9d surface, and sodium hydroxide in the slurry tends to crystallize. The resulting solidified slurry particles may fall off the conditioner head onto the polishing pad. These particles may scratch the wafer during polishing. The CMP apparatus can include a cleaning cup for removing slurry deposits from a conditioner head. Unfortunately, some wafer scratching persists.
The slurry solidification problem has been associated generally with the abrasive disk of the conditioner head since it is the part of the conditioner head that physically contacts the polishing pad. In reality, the slurry may be splashed on other parts of the conditioner head, e.g., a top side of the conditioner head.
In view of the above, there is room for improvement in cleaning of the conditioner head.
In general, in one aspect, the present invention features a chemical mechanical polishing apparatus including a pad conditioner having a conditioner head, and a cleaning cup having a base and a wall extending upward from the base for receiving and cleaning the conditioner head. The cleaning cup includes a spray nozzle to spray a cleaning fluid onto the conditioner head.
Implementations of the invention may include one or more of the following features. The cleaning cup further includes a first passage for directing the cleaning fluid to the spray nozzle. The cleaning cup further includes a spray nozzle support having a second passage. The spay nozzle support supports the spray nozzle. The first passage is connected to the second passage to direct the cleaning fluid to the spray nozzle. The cleaning cup further includes a cleaning solution passage for continuously supplying the cleaning cup with a cleaning solution. The cleaning cup further includes at least one drain to drain the cleaning solution from the cleaning cup. The cleaning solution in the cleaning cup is maintained at a substantially constant level. The cleaning cup further includes a plurality of support pins extending upward from the base to support the conditioner head thereon and provide a space between the conditioner head and the base for the flow of cleaning solution therebetween. The cleaning fluid may be deionized water or air. The cleaning cup includes a plurality of spray nozzles. The spray nozzle sprays a cleaning fluid on a top side of the conditioner head.
In another aspect, a chemical mechanical polishing apparatus includes a pad conditioner having a conditioner head, a cleaning cup having a base and a wall extending upward from the base for receiving and cleaning the conditioner head and a cleaning fluid dispenser to provide a flowing cleaning fluid to a top side of the conditioner head.
In another aspect, the invention is a method of cleaning a chemical mechanical polishing apparatus. In the method, a conditioner head of a pad conditioner is placed in a cleaning cup, and a cleaning fluid is provided to a top side of the conditioner head.
Implementations of the invention may include the following. The cleaning fluid may be provided to a drive shaft or an arm of the pad conditioner.
In another aspect, the invention is a chemical mechanical polishing apparatus which includes a pad conditioner having a conditioner head, a cleaning cup having a base and a wall extending upward from the base for receiving and cleaning the conditioner head, and a plurality of fluid dispensers to dispense a cleaning fluid onto the conditioner head and another part of the pad conditioner.
Implementations of the invention may include one or more of the following features. One of the fluid dispensers may be placed on the base of the cleaning cup to face a bottom side of the conditioner head. The cleaning fluid may be dispensed to a shaft of the pad conditioner. The pad conditioner and the cleaning cup may be mounted on a table top and at least one of the fluid dispensers may be placed on the table top to dispense the cleaning fluid on an arm of the pad conditioner.
In another aspect, the invention is a chemical mechanical polishing apparatus which includes a pad conditioner having a conditioner head, a cleaning cup having a base and a wall extending upward from the base for receiving and cleaning the conditioner head, and a fluid dispenser placed on the base of the cleaning cup to spray a cleaning fluid toward a bottom side of the conditioner head placed in the cleaning cup.
In another aspect, the invention is directed to a method of cleaning a chemical mechanical polishing apparatus in which a conditioner head of a pad conditioner is placed in a cleaning cup, and a cleaning fluid is provided to the conditioner head and another part of the pad conditioner.
Advantages of the invention may include one or more of the following. The invention provides a cleaning apparatus which can clean the entire conditioner head. The invention also provides a reliable means of cleaning an abrasive disk without undue risk of contaminating the abrasive disk. The invention also provides a cleaning apparatus which can clean other parts of the pad conditioner.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments, and from the claims.